1. Field of the Invention
The present invention generally relates to light signals and, more particularly, to Light Emitting Diode (LED) traffic signals having optics that have uniform light intensity over an emitted surface.
2. Description of Related Art
Light Emitting Diode (LED) signals such as LED traffic signals, pedestrian walk-way signals, arrow signals, alphanumeric signals, etc. present numerous advantages over incandescent lamp signals. For instance, a LED consumes relatively less power and is associated with relatively longer life than an incandescent light source. The longer life typically leads to improved reliability and lower maintenance costs.
Conventional LED signals typically use multiple LEDs in an array to replicate the light output of the incandescent lamp. For example, a sufficient number of LEDs are incorporated into the signal to create and fill the shape of the symbol (e.g., a hand, a man-walking, etc.) displayed by the signal. However, such conventional signals usually do not create a uniform light surface. As a consequence, one or more of the LEDs, or the individual points of light from each LED, are discernable within the light surface. Such signals are often referred to as “dotted signals” and can create a display aspect that is visually displeasing. If one or more LED burns out, a void may be left in the appearance of the signal. Further, if the LEDs are not closely matched in intensity and color the resultant appearance may be non-homogenous.
Each generation of LEDs typically is brighter. As a result, fewer LEDs are needed within a traffic signal in order to provide a relatively similar light appearance. Using fewer LEDs can reduce the cost of the signal. However, using fewer LEDs can also increase the potential for viewing the LEDs as individual point sources and for creating undesirable shadows in non-illuminate areas.